/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/************************************************************************
 * libc/misc/lib_filesem.c
 *
 *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ************************************************************************/

/************************************************************************
 * Included Files
 ************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <unistd.h>
#include <semaphore.h>
#include <errno.h>
#include <assert.h>

#include "lib_internal.h"

#if CONFIG_STDIO_BUFFER_SIZE > 0

/************************************************************************
 * Pre-processor Definitions
 ************************************************************************/

/************************************************************************
 * Private Data
 ************************************************************************/

/************************************************************************
 * Global Functions
 ************************************************************************/

/************************************************************************
 * lib_sem_initialize
 ************************************************************************/

void lib_sem_initialize(FAR struct file_struct *stream)
{
	/* Initialize the LIB semaphore to one (to support one-at-a-time access
	 * to private data sets.
	 */

	(void)sem_init(&stream->fs_sem, 0, 1);

	stream->fs_holder = -1;
	stream->fs_counts = 0;
}

/************************************************************************
 * lib_take_semaphore
 ************************************************************************/

void lib_take_semaphore(FAR struct file_struct *stream)
{
	pid_t my_pid = getpid();

	/* Do I already have the semaphore? */

	if (stream->fs_holder == my_pid) {
		/* Yes, just increment the number of references that I have */

		stream->fs_counts++;
	} else {
		/* Take the semaphore (perhaps waiting) */

		while (sem_wait(&stream->fs_sem) != 0) {
			/* The only case that an error should occr here is if the wait
			 * was awakened by a signal.
			 */

			ASSERT(get_errno() == EINTR);
		}

		/* We have it.  Claim the stak and return */

		stream->fs_holder = my_pid;
		stream->fs_counts = 1;
	}
}

/************************************************************************
 * lib_give_semaphore
 ************************************************************************/

void lib_give_semaphore(FAR struct file_struct *stream)
{
	pid_t my_pid = getpid();

	/* I better be holding at least one reference to the semaphore */

	ASSERT(stream->fs_holder == my_pid);

	/* Do I hold multiple references to the semphore */

	if (stream->fs_counts > 1) {
		/* Yes, just release one count and return */

		stream->fs_counts--;
	} else {
		/* Nope, this is the last reference I have */

		stream->fs_holder = -1;
		stream->fs_counts = 0;
		ASSERT(sem_post(&stream->fs_sem) == 0);
	}
}
#endif							/* CONFIG_STDIO_BUFFER_SIZE */
